// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MEDIA_BASE_TEST_RANDOM_H_
#define MEDIA_BASE_TEST_RANDOM_H_

#include <stdint.h>

#include "base/logging.h"

// Vastly simplified ACM random class meant to only be used for testing.
// This class is meant to generate predictable sequences of pseudorandom
// numbers, unlike the classes in base/rand_util.h which are meant to generate
// unpredictable sequences.
// See
// https://code.google.com/p/szl/source/browse/trunk/src/utilities/acmrandom.h
// for more information.

namespace media {

class TestRandom {
public:
    explicit TestRandom(uint32_t seed)
    {
        seed_ = seed & 0x7fffffff; // make this a non-negative number
        if (seed_ == 0 || seed_ == M) {
            seed_ = 1;
        }
    }

    int32_t Rand()
    {
        static const uint64_t A = 16807; // bits 14, 8, 7, 5, 2, 1, 0
        seed_ = static_cast<int32_t>((seed_ * A) % M);
        CHECK_GT(seed_, 0);
        return seed_;
    }

private:
    static const uint64_t M = 2147483647L; // 2^32-1
    int32_t seed_;
};

} // namespace media

#endif // MEDIA_BASE_TEST_RANDOM_H_
